Bio-based products must have comparable or superior characteristics as compared to conventional products to be competitive and accepted in the marketplace. Bio-based lubricants, in particular, must have low pour point temperatures, desirable viscosity, and thermal stability, for example, to be viable alternatives to petroleum-based products. Vegetable oils alone are a functional lubricant; however, they typically have low resistance to thermal oxidative stability (see e.g., Becker, R. & Knorr, A., 1996. An evaluation of antioxidants for vegetable oils at elevated temperatures. Lubr. Sci. 8, 95-117) and poor low temperature performance (see e.g., Asadauskas, S. & Erhan, S. Z., 1999. Depression of pour points of vegetable oils by blending with diluents used for biodegradable lubricants. J. Am. Oil Chem. Soc. 76, 313-316; Zehler, G. R., 2001. Performance tiering of biodegradable hydraulic fluids. Lubricants World September, 22-26). These desired properties sometimes can be improved with additives, but at the expense of biodegradability, toxicity, and price.
With increasing demand for bio-based materials, weaknesses in performance and physical characteristics must be overcome for effective application in industrial and commercial environments. Synthetic esters, such as polyol esters and adipates, low viscosity poly alpha olefins (PAO), such as PAO 2, vegetable oils, especially canola oil, and oleates, for instance, are used industrially as biodegradable basestocks to formulate lubricants. Lubricants usually contain 80-100 wt % basestock and 0-20 wt % additives to tailor viscometric properties, low temperature behavior, oxidative and thermal stability, corrosion protection, demulsibility and water rejection, friction coefficients, lubricities, wear protection, air release, color, and other properties. Biodegradability, however, cannot be improved by using additives.
Estolide compositions have overcome some of these shortcomings without the addition of expensive additives/adjuvants and have shown great promise for use in a wide variety of products with varying physical properties, such as edible applications, cooling fluids, cosmetics, hydraulic fluids, inks, crankcase lubricants, and coatings, among other applications. Nonetheless, there still exists an ongoing need for further improved high-performance bio-based products formulated with renewable agricultural materials (e.g., plant-based oils and animal-based oils) that are economically feasible and sustainable. There is a particular need for such products that exhibit high performance in cold weather applications and thermally harsh conditions.